1. Field of the Invention
The present invention relates to a directional antenna, and in particular to a directional antenna which is implemented in electronic devices.
2. Description of Related Art
Directional antennas are usually implemented in electronic devices or adapted in the electronic devices, and they can transmit or receive electromagnetic waves in a predetermined direction. After electrical signals of the electronic devices are converted into electromagnetic waves, the electromagnetic waves are transmitted through the directional antennas. In addition, the electromagnetic waves are received through the directional antennas, and then converted into electrical signals for electronic devices. Because the directional antennas transmit or receive electromagnetic waves much more in one direction than other directions, the directional antennas are suitable for signal transmission over a long distance. In this light, the directional antennas are usually used to transmit or receive electrical signals with satellites or long distance antennas.
For example, an electronic device with a global positioning system (GPS) utilizes a directional antenna to transmit/receive signals over long distance. The electronic device is usually a portable electronic device such as mobile phone. The position of the portable electronic device changes when user has different postures, and the satellite orbits around the earth. In addition, the directional antenna of GPS must be continuously directed toward the satellite so it is difficult in the prior art.
Users manually adjust the directional of the antenna in the prior art when the directional antenna does not performs very well so that the antenna is tuned to a better direction. To overcome this drawback, an omni-directional antenna is utilized and suitable for signal transmission over a long distance without manual adjustment to the antenna.
Thus, there is a need for a directional antenna which is implemented in an electronic device and properly directed toward a direction to overcome the above drawbacks.